Identification of a sub-population of B cells that proliferates after infection with Epstein-Barr virus

Optimizing the method for expressing human monoclonal antibodies from a single peripheral blood cell from vaccinated donors

Human monoclonal antibodies are essential diagnostic and research tools and one of the most promising therapeutics. In the past years, single B cell technologies have evolved and over-come conventional methods' limitations, enabling the isolation of scarce B cell populations with desirable characteristics. In this study, we describe a simple and efficient method to isolate anti-gen-specific plasmablasts and memory B cells from hepatitis B virus vaccinated donors' peripheral blood and consequently amplification of immunoglobulin variable region genes. Amplified immunoglobulin variable region genes were cloned into expression vectors and transfected into a human cell line to produce human recombinant monoclonal antibodies. Major challenges in this protocol were isolation of antigen-specific B cells based on surface markers, recovering mRNA from a single cell for efficient amplification, and cloning the correct insert into a desired expression vector. The essential feature of our protocol was the separation of B cells from peripheral blood mononuclear cells before sorting. We identified antigen-specific binding B cells based on the expression of surface markers CD19, CD27, IgG, and binding to hepatitis B surface antigen. Efficient single-cell reverse transcription and polymerase chain reaction (RT-PCR) were achieved using a random primer mix and Kapa Hifi Hot Start Polymerase. Amplification efficiency differed among heavy and light chain variable regions (highest at heavy chain (68 %) and lowest at lambda light chain (22 %)). After co-transfection of HEK293T/17 with successfully cloned heavy and light chain vectors, 70 % of transfected cells produced recombinant monoclonal antibodies at a concentration ∼ 4 μg/ml and 7 % of them showed binding to HBsAg. Human monoclonal antibodies from peripheral blood have advantages over antibodies of mouse origin or phage display libraries, because of their high specificity and self-tolerance. Using the described protocol, we can generate fully human monoclonal antibodies to any other antigen for application in immunotherapy or basic research.

Lymphoblastoid cell lines do not recapitulate physiological circulating B cell subtypes

Lymphoblastoid cell lines (LCLs) are immortalised peripheral B lymphocytes, transformed via infection with Epstein Barr virus (EBV). The use of LCLs to study B cell function remains controversial and core markers to define physiological B cell populations are not consistent between studies of physiological B cells and LCLs. A consensus on the nature of these commonly used cell lines has not been reached. Recently, a core set of markers to subtype peripheral B cells was proposed, addressing the lack of agreed markers for B cell characterisation. In this present study, the consensus panel was applied to describe the B cell subtypes in LCLs. We found that LCLs were generally not physiologically representative of B cells, with most cells harbouring marker combinations absent on peripheral B cells. Some B cell subtyping markers were fundamentally altered during EBV transformation to LCLs (e.g. CD19, CD21). Notably, most LCLs secreted IgG but the associated marker combinations were predominantly only present in vitro following EBV transformation. This study therefore informs interpretation of past investigations, and planning of future studies using LCLs, as these cells are unlikely to behave like their pre-transformed B cell subtype.

Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

Transcriptome alterations in peripheral blood B cells of patients with multiple sclerosis receiving immune reconstitution therapy

BACKGROUND

Multiple sclerosis (MS) is a chronic, inflammatory and neurodegenerative disease that leads to irreversible damage to the brain and spinal cord. The goal of so-called "immune reconstitution therapies" (IRTs) is to achieve long-term disease remission by eliminating a pathogenic immune repertoire through intense short-term immune cell depletion. B cells are major targets for effective immunotherapy in MS.

OBJECTIVES

The aim of this study was to analyze the gene expression pattern of B cells before and during IRT (i.e., before B-cell depletion and after B-cell repopulation) to better understand the therapeutic effects and to identify biomarker candidates of the clinical response to therapy.

METHODS

B cells were obtained from blood samples of patients with relapsing-remitting MS (n = 50), patients with primary progressive MS (n = 13) as well as healthy controls (n = 28). The patients with relapsing MS received either monthly infusions of natalizumab (n = 29) or a pulsed IRT with alemtuzumab (n = 15) or cladribine (n = 6). B-cell subpopulation frequencies were determined by flow cytometry, and transcriptome profiling was performed using Clariom D arrays. Differentially expressed genes (DEGs) between the patient groups and controls were examined with regard to their functions and interactions. We also tested for differences in gene expression between patients with and without relapse following alemtuzumab administration.

RESULTS

Patients treated with alemtuzumab or cladribine showed on average a > 20% lower proportion of memory B cells as compared to before IRT. This was paralleled by profound transcriptome shifts, with > 6000 significant DEGs after adjustment for multiple comparisons. The top DEGs were found to regulate apoptosis, cell adhesion and RNA processing, and the most highly connected nodes in the network of encoded proteins were ESR2, PHB and RC3H1. Higher mRNA levels of BCL2, IL13RA1 and SLC38A11 were seen in patients with relapse despite IRT, though these differences did not pass the false discovery rate correction.

CONCLUSIONS

We show that B cells circulating in the blood of patients with MS undergoing IRT present a distinct gene expression signature, and we delineated the associated biological processes and gene interactions. Moreover, we identified genes whose expression may be an indicator of relapse risk, but further studies are needed to verify their potential value as biomarkers.

Feeder Cells at the Interface of Natural Killer Cell Activation, Expansion and Gene Editing

Genome engineered natural killer (NK) cell therapies are emerging as a promising cancer immunotherapy platform with potential advantages and remaining uncertainties. Feeder cells induce activation and proliferation of NK cells via cell surface receptor-ligand interactions, supported by cytokines. Feeder cell expanded NK cell products have supported several NK cell adoptive transfer clinical trials over the past decade. Genome engineered NK cell therapies, including CAR-NK cells, seek to combine innate and alloreactive NK cell anti-tumor activity with antigen specific targeting or additional modifications aimed at improving NK cell persistence, homing or effector function. The profound activating and expansion stimulus provided by feeder cells is integral to current applications of clinical-scale genome engineering approaches in donor-derived, primary NK cells. Herein we explore the complex interactions that exist between feeder cells and both viral and emerging non-viral genome editing technologies in NK cell engineering. We focus on two established clinical-grade feeder systems; Epstein-Barr virus transformed lymphoblastoid cell lines and genetically engineered K562.mbIL21.4-1BBL feeder cells.

Propagation of EBV-driven Lymphomatous Transformation of Peripheral Blood B Cells by Immunomodulators and Biologics Used in the Treatment of Inflammatory Bowel Disease

BACKGROUND

Immunomodulators and anti tumor-necrosis-α antibodies (anti-TNFs) have been implicated in increased risk of Epstein-Barr virus (EBV)-driven B-cell lymphoproliferative disorders in inflammatory bowel disease (IBD) patients. However, the underlying mechanisms are poorly understood.

METHODS

An in-vitro model of lymphoblastoid cell line (LCL) was established by co-incubation of EBV-infected human peripheral blood mononuclear cells (PBMC) with Cyclosporin-A (CSA). After 4 weeks, the resultant LCLs were analyzed by flow cytometry, telomerase activity assay, and next generation sequencing. Subsequently, LCLs were explored in the presence of therapeutic agents for IBD (anti-TNFs, vedolizumab, 6-Mercaptopurine [6MP], methotrexate). Epstein-Barr virus titers were quantitated by real-time polymerase chain reaction.

RESULTS

In cultures of PBMC with EBV and CSA, LCLs were characterized as an expanded, long lived population of CD58+CD23hi B-cells with high telomerase activity and clonal expansion. Upon addition to the cell cultures, LCL percentages were higher with infliximab (median 19.21%, P = 0.011), adalimumab (median 19.85%, P = 0.003), and early washed-out 6MP (median 30.57%, P = 0.043) compared with PBMC with EBV alone (median 9.61%). However, vedolizumab had no such effect (median 8.97%; P = 0.435). Additionally, LCL expansion was accompanied by increase in intracellular, rather than extracellular, EBV viral copies. Compared with PBMC with EBV alone, high levels of LCL were subsequently observed after triple depletion of NK cells, CD4+ T cells, and CD8+ T cells (median 52.8% vs 16.4%; P = 0.046) but also in cultures depleted solely of CD4+ T cells (median 30.7%, P = 0.046).

CONCLUSIONS

These results suggest that both anti-TNFs and 6MP, but not vedolizumab, propagate EBV-driven lymphoblastoid transformation in an in vitro model of lymphoma. This model may prove useful for studying mechanisms underlying proneoplastic viral immune interactions of novel drugs in IBD therapy.

Epstein-Barr Virus- (EBV-) Immortalized Lymphoblastoid Cell Lines (LCLs) Express High Level of CD23 but Low CD27 to Support Their Growth

Epstein-Barr virus (EBV) is one of the common human herpesvirus types in the world. EBV is known to infect more than 95% of adults in the world. The virus mainly infects B lymphocytes and could immortalize and transform the cells into EBV-bearing lymphoblastoid cell lines (LCLs). Limited studies have been focused on characterizing the surface marker expression of the immortalized LCLs. This study demonstrates the generation of 15 LCLs from sixteen rheumatoid arthritis (RA) patients and a healthy volunteer using B95-8 marmoset-derived EBV. The success rate of LCL generation was 88.23%. All CD19+ LCLs expressed CD23 (16.94-58.9%) and CD27 (15.74-80.89%) on cell surface. Our data demonstrated two distinct categories of LCLs (fast- and slow-growing) (p<0.05) based on their doubling time. The slow-growing LCLs showed lower CD23 level (35.28%) compared to fast-growing LCLs (42.39%). In contrast, the slow-growing LCLs showed higher percentage in both CD27 alone and CD23+CD27+ in combination. Overall, these findings may suggest the correlations of cellular CD23 and CD27 expression with the proliferation rate of the generated LCLs. Increase expression of CD23 may play a role in EBV immortalization of B-cells and the growth and maintenance of the EBV-transformed LCLs while CD27 expression might have inhibitory effects on LCL proliferation. Further investigations are warranted to these speculations.

Application of Epstein-Barr Virus for Optimization of Immortalized B-lymphocyte Production as a Positive Control in Genetic Studies

BACKGROUND

Infection of B-cells with Epstein-Barr virus (EBV) leads to more and subsequent immortalization. This is considered as the method of choice for generating lymphoblastoid cell lines (LCLs). Producing LCLs, although very useful but is very time consuming and troublesome, drives the requirement for quicker and more reliable methods for EBV-driven B-cell transformation.

MATERIALS AND METHODS

After successfully production of LCLs, different parameters including temperature, serum concentration, type of culture medium, and CO₂ concentration were evaluated on EBV-transformed B-cells. In this study, we were able to produce LCLs and optimize condition.

RESULTS

The best condition for generating LCLs was 37°C, 5% CO₂, 20% fasting blood sugar, and RPMI 1640. The study results were to establish a reliable method for producing LCLs that can be used to produce immortalized B-cells from almost any sources.

CONCLUSION

This can help with tumorgenecity studies, as well as producing control material for rare genetic disorders and so on. The aim of this study was to determine optimized condition for reliable and reproducible LCLs from different sources.

A CD2 high-expressing stress-resistant human plasmacytoid dendritic-cell subset

Human plasmacytoid dendritic cells (pDCs) were considered to be a phenotypically and functionally homogeneous cell population; however, recent analyses indicate potential heterogeneity. This is of major interest, given their importance in the induction of anti-viral responses and their role in creating immunologically permissive environments for human malignancies. For this reason, we investigated the possible presence of human pDC subsets in blood and bone marrow, using unbiased cell phenotype clustering and functional studies. This defined two major functionally distinct human pDC subsets, distinguished by differential expression of CD2. The CD2(hi) and CD2(lo) pDCs represent discontinuous subsets, each with hallmark pDC functionality, including interferon-alpha production. The rarer CD2(hi) pDC subset demonstrated a significant survival advantage over CD2(lo) pDC during stress and upon exposure to glucocorticoids (GCs), which was associated with higher expression of the anti-apoptotic molecule BCL2. The differential sensitivity of these two human pDC subsets to GCs is demonstrated in vivo by a relative increase in CD2(hi) pDC in multiple myeloma patients treated with GCs. Hence, the selective apoptosis of CD2(lo) pDC during stress represents a novel mechanism for the control of innate responses.

B lymphocytes from patients with a hypomorphic mutation in STAT3 resist Epstein-Barr virus-driven cell proliferation

Epstein-Barr virus (EBV) oncogenes exert potent B cell proliferative effects. EBV infection gives rise to B cell lines that readily proliferate in culture. This ability of EBV represents a powerful tool to study cell proliferation. In efforts to delineate the contribution of signal transducer and activator of transcription 3 (STAT3) toward EBV-driven cell proliferation, we have discovered that B cells from patients with autosomal dominant hyper-IgE syndrome (AD-HIES) resist such EBV oncogene-driven outgrowth of cells. Patients with AD-HIES have a dominant negative mutation in their STAT3 gene which renders most of the protein nonfunctional. Exposure of healthy subject-derived B cells to EBV resulted in early activation of STAT3, rapidly followed by increased expression of its mRNA and protein. STAT3 upregulation preceded the expression of EBNA2, temporally one of the first viral oncogenes to be expressed. We found that STAT3 was necessary for subsequent survival and for proliferation of EBV-infected cells past the S phase of the cell cycle. Consequently, B cells from AD-HIES patients were prone to dying and accumulated in the S phase, thereby accounting for impaired cell outgrowth. Of importance, we have now identified a cohort of patients with a primary immunodeficiency disorder whose B cells oppose EBV-driven proliferative signals. These findings simultaneously reveal how EBV manipulates host STAT3 even before expression of viral oncogenes to facilitate cell survival and proliferation, processes fundamental to EBV lymphomagenesis.

Establishment of Epstein-Barr virus growth-transformed lymphoblastoid cell lines

Infection of B cells with Epstein-Barr virus (EBV) leads to proliferation and subsequent immortalization, resulting in establishment of lymphoblastoid cell lines (LCL) in vitro. Since LCL are latently infected with EBV, they provide a model system to investigate EBV latency and virus-driven B cell proliferation and tumorigenesis(1). LCL have been used to present antigens in a variety of immunologic assays(2, 3). In addition, LCL can be used to generate human monoclonal antibodies(4, 5) and provide a potentially unlimited source when access to primary biologic materials is limited(6, 7). A variety of methods have been described to generate LCL. Earlier methods have included the use of mitogens such as phytohemagglutinin, lipopolysaccharide(8), and pokeweed mitogen(9) to increase the efficiency of EBV-mediated immortalization. More recently, others have used immunosuppressive agents such as cyclosporin A to inhibit T cell-mediated killing of infected B cells(7, 10-12). The considerable length of time from EBV infection to establishment of cell lines drives the requirement for quicker and more reliable methods for EBV-driven B cell growth transformation. Using a combination of high titer EBV and an immunosuppressive agent, we are able to consistently infect, transform, and generate LCL from B cells in peripheral blood. This method uses a small amount of peripheral blood mononuclear cells that are infected in vitroclusters of cells can be demonstrated. The presence of CD23 with EBV in the presence of FK506, a T cell immunosuppressant. Traditionally, outgrowth of proliferating B cells is monitored by visualization of microscopic clusters of cells about a week after infection with EBV. Clumps of LCL can be seen by the naked eye after several weeks. We describe an assay to determine early if EBV-mediated growth transformation is successful even before microscopic clusters of cells can be demonstrated. The presence of CD23(hi)CD58(+) cells observed as early as three days post-infection indicates a successful outcome.